Hammer drill

ABSTRACT

An intermediate shaft  3  operatively coupled to a motor and a tool holding sleeve  11  for holding a tip end tool  22  are disposed in a housing  1  in parallel with each other. A motion converting member  5  for converting rotary motion to reciprocating motion thereby to operate the tip end tool  22  to hammer is rotatably provided on the intermediate shaft  3 . A first clutch  6  is provided between the intermediate shaft  3  and the motion converting member  5 . A clutch sleeve  25  which is coupled to the intermediate shaft  3  by way of a rotation transmitting member, and a second clutch  27  which rotates integrally with the tool holding sleeve  11  and can move in a longitudinal direction of the tool holding sleeve are arranged on an outer periphery of the tool holding sleeve  11 . The second clutch  27  is provided so as to be engaged with and disengaged from the clutch sleeve  25.

TECHNICAL FIELD

The present invention relates to a hammer drill in which motion mode can be switched between a hammering mode, a rotation mode, and a rotary hammering mode.

BACKGROUND ART

Generally, a hammer drill can transmit impact and rotation from a motor to a tool provided at its tip end by way of a hammering mechanism and a rotary driving mechanism, at the same time, or independently from each other, by operating an operating lever to rotate and selecting either of a hammering mode, a rotation mode and a rotary hammering mode.

In the above described hammer drill, selection of the motion mode is carried out by a mode switching mechanism. The motion mode switching mechanism is so constructed that the hammering mechanism and the rotary driving mechanism are respectively provided with clutches, thereby to connect or disconnect the rotating force from the motor to the hammering mechanism or the rotary driving mechanism.

Specifically, the mode switching mechanism which is so constructed that an intermediate shaft operatively coupled to the motor and a tool holding sleeve for holding the tip end tool are disposed in a housing in parallel with each other, and the tool holding sleeve can be operatively coupled to the hammering mechanism and the rotary driving mechanism by way of the intermediate shaft has been known. In this mechanism, the intermediate shaft is provided with two clutches, one of which transmits or interrupts a torque of the intermediate shaft to the hammering mechanism, and the other clutch transmits the torque to the rotary driving mechanism. The second clutch moves in an axial direction of the intermediate shaft thereby to be engaged with and disengaged from the driving gear which is provided on the tool holding sleeve. The above described mechanism is disclosed in U.S. Pat. No. 6,109,364.

In the above described mode switching mechanism, in the pure hammering mode, the second clutch moves in a direction separating from the driving gear along the intermediate shaft against an urge of a spring, and in the rotation mode, the second clutch returns to be engaged with the driving gear. Therefore, when the motion mode is switched from the pure hammering mode to the rotation mode, the gear of the second clutch which has been disengaged is moved by the urge of the spring to be reengaged with the driving gear. Accordingly, there is such anxiety that in case where the driving gear rotates, the gear may be damaged, because reengagement with the driving gear becomes difficult, or a sudden transmitting force by the reengagement is exerted on the driving gear.

DISCLOSURE OF THE INVENTION

One or more embodiments of the invention provide a hammer drill which can ensure smooth operation, with no problem of engagement between gears, even in case where motion mode is switched from a pure hammering mode to a rotation mode.

According to one or more embodiments of the invention, an intermediate shaft operatively coupled to a motor and a tool holding sleeve for holding a tip end tool are disposed in a housing in parallel with each other, a motion converting member for converting rotary motion to reciprocating motion thereby to operate the tip end tool to hammer is rotatably provided on the intermediate shaft, a first clutch is provided between the intermediate shaft and the motion converting member, a clutch sleeve coupled to the intermediate shaft by way of a rotation transmitting member and a second clutch which rotates integrally with the tool holding sleeve and can move in a longitudinal direction of the tool holding sleeve are arranged on an outer periphery of the tool holding sleeve, and the second clutch is provided so as to be engaged with and disengaged from the clutch sleeve.

In the above described hammer drill, the intermediate shaft and the tool holding sleeve are arranged in parallel, and operatively connected to each other by means of gears. The first clutch is provided at a side of the intermediate shaft, while the second clutch is provided at a side of the tool holding sleeve, and the rotation transmitting member and the clutch sleeve are interposed between the intermediate shaft and the second clutch. Therefore, rotation of the intermediate shaft is always transmitted to the clutch sleeve, and no problem of engagement occurs in this region.

Moreover, because the second clutch can rotate integrally with the tool holding sleeve, and can move along the longitudinal direction of the tool holding sleeve, the second clutch and the tool holding sleeve always rotate together in the engaged state, and no problem of engagement occurs.

Accordingly, it is possible to secure smooth operation irrespective of switching between the motion modes.

Moreover, the housing may be provided with a lock member capable of being engaged with the second clutch which has been disengaged from the clutch sleeve, and it is possible to urge this lock member so as to be engaged with the second clutch.

In this case, because the lock member is urged by a spring so as to be engaged, even when the second clutch is separated from the clutch sleeve, the second clutch is rapidly locked by the lock member, whereby the rotation of the tool holding sleeve can be reliably stopped.

Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of an essential part of a hammer drill in rotary hammering mode.

FIG. 2 is a longitudinal sectional view of the essential part of the hammer drill in rotation mode.

FIG. 3 is a longitudinal sectional view of the essential part of the hammer drill in hammering mode.

FIG. 4 is a sectional view taken along a line A-A in FIG. 1.

FIG. 5A is a sectional view taken along a line B-B in FIG. 1.

FIG. 5B is a sectional view taken along a line C-C in FIG. 5A.

FIG. 6 is an explanatory view showing relative engagement between a lock bar and a second clutch.

FIG. 7 is an overall view of the hammer drill showing a switch lever.

FIG. 8 is a sectional view taken along a line D-D in FIG. 7.

FIG. 9 is a plan view showing relative engagement between a shift plate and the second clutch.

FIG. 10 is a sectional view taken along a line E-E in FIG. 9.

DESCRIPTION OF THE REFERENCE SIGNS

-   1 Housing -   3 Intermediate shaft -   5 Motion converting member -   6 First clutch -   11 Tool holding sleeve -   22 Tip end tool -   25 Clutch sleeve -   27 Second clutch

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a longitudinal sectional view of an essential part of a hammer drill. In this drawing, numeral 1 represents a housing. A motor (not shown) is contained in rear of the housing 1 (at a right side in FIG. 1). An output shaft 2 of the motor is pivotally held by an inner housing 1 a which is assembled to an inside of the housing 1, and meshed with a reduction gear 4 of an intermediate shaft 3 which is pivotally held in parallel with the output shaft 2. A motion converting member 5 having a spherical face is rotatably mounted on the intermediate shaft 3. A spline 7 b provided on the motion converting member 5 and a spline 8 of a first clutch 6 are arranged so as to rotate and so as to move in an axial direction. The first clutch 6 is urged to move forward by a clutch spring 9 so as to be engaged with a spline 7 a of the intermediate shaft 3. Moreover, a first gear 10 is provided on a front end of the intermediate shaft 3.

A tool holding sleeve 11 is rotatably provided in the housing 1 in parallel with the intermediate shaft 3.

A piston 12 in a bottomed cylindrical shape is slidably contained in the tool holding sleeve 11.

A backward end of the piston 12 is coupled to the motion converting member 5 outside the intermediate shaft 3 by way of a swing shaft 16 which is provided with a reciprocating bearing 15. A ball 19 is engaged between a groove 17 formed on an inner periphery of the reciprocating bearing 15 and a groove 18 which is diagonally formed in the motion converting member 5. Accordingly, when the motion converting member 5 rotates, this rotation is converted to back and forth swing motions of the swing shaft 16.

A first hammer 20 is slidably disposed inside the piston 12, and a second hammer 21 is disposed in front of the first hammer 20. Further, a tip end tool 22 such as a drill bit is provided in front of the second hammer 21. The second hammer 21 and the tip end tool 22 are fitted in a small diameter part 11 a of the tool holding sleeve 11 so as to slide in a certain range. A ball 24 projected from a through hole 29 in the small diameter part is engaged with a key groove 23 which is formed in a base part of the tip end tool 22. Accordingly, the tip end tool 22 rotates integrally with the tool holding sleeve 11, and at the same time, can move back and forth along a longitudinal direction of the tool holding sleeve 11.

A clutch sleeve 25, a second gear 26 (a rotation transmitting member 26), and a second clutch 27 are provided outside the tool holding sleeve 11.

The clutch sleeve 25 which has a large diameter part 30 formed at its back end by way of a flange 28 is rotatably provided around the tool holding sleeve 11. As shown in FIG. 4, engaging claws 31 are formed on an inner face of the large diameter part 30.

The second gear 26 is always meshed with the first gear 10 of the intermediate shaft 3, and rotatably provided on an outer periphery of the clutch sleeve 25. The second gear 26 and the flange 28 are respectively provided with slanted convex parts 32 and slanted concave parts 33 which are opposed to each other, as shown in FIGS. 5A and 5B, and urged by a clutch spring 34 so as to be meshed with each other. Rotation of the second gear 26 is transmitted to the clutch sleeve 25. The engaging claws 31 of the clutch sleeve 25 are so adapted as to be meshed with the teeth of the second clutch 27.

The second clutch 27 has front teeth 36 and rear teeth 37 which are formed on an outer peripheral face thereof, interposing an engaging groove 35 in the middle. The front teeth 36 are urged by a clutch spring 39 so as to be meshed with the engaging claws 31.

Moreover, the second clutch 27 is provided with a key 40, while the tool holding sleeve 11 is provided with a key groove 41, and the second clutch 27 is coupled to the tool holding sleeve 11 by engagement between the key 40 and the key groove 41. Accordingly, the second clutch 27 rotates integrally with the tool holding sleeve 11, and at the same time, can slide along the longitudinal direction of the tool holding sleeve 11, whereby the second clutch 27 can be engaged with and disengaged from the clutch sleeve 25.

Further, a lock bar 42 as a lock member is disposed in rear of the second clutch 27 inside the housing 1 so as to move back and forth in the same manner as the second clutch. The lock bar 42 is urged by a spring 43 so as to move toward the second clutch 27. The lock bar 42 is provided with teeth 44 at a front end thereof, in such a manner that when the second clutch 27 is disengaged from the clutch sleeve 25 and moved backward, the teeth 44 may be engaged with the rear teeth 37 of the second clutch 27.

Then, operation of the hammer drill having the above described structure will be described. Firstly, FIG. 1 shows the hammer drill in the rotary hammering mode, in which the motion converting member 5 is coupled to the intermediate shaft 3 by the engagements between the splines 7 a, 7 b and 8, and the clutch sleeve 25 is coupled to the tool holding sleeve 11 by means of the second clutch 27. In this mode, when the motor rotates, as a first step, the rotation force is transmitted from the output shaft 2 to the intermediate shaft 3 by way of the reduction gear 4. Rotation torque of the intermediate shaft 3 is transmitted to the motion converting member 5 by way of the first clutch 6. Along with the rotation of the motion converting member 5, the swing shaft 16 swings, and the swing motion is converted to reciprocating motion of the piston 12. When the piston 12 reciprocates back and forth, air in a space S behind the first hammer 20 inside the piston 12 is compressed, whereby the first hammer 20 moves back and forth to strike the second hammer 21, and then, the second hammer 21 strikes the tip end tool 22. In this manner, a hammering force is transmitted to the tip end tool 22 which is pressed against an object such as a concrete block.

The rotation torque of the intermediate shaft 3 is also transmitted to the clutch sleeve 25 by way of the first gear 10 and the second gear 26. The rotation of the clutch sleeve 25 is further transmitted to the tool holding sleeve 11 by way of the second clutch 27, whereby the tip end tool 22 is also rotated.

In this manner, in the above described rotary hammering mode, the hammering motion and the rotary motion of the hammer are carried out, whereby the hammering force and the rotation force are transmitted to the tip end tool.

Then, FIG. 2 shows the hammer drill in the rotation mode. In this mode, when the first clutch 6 retreats against the urge of the clutch spring 9, the spline 7 a is disengaged from the spline 8, whereby transmission of the motion from the intermediate shaft 3 to the motion converting member 5 is interrupted, and hence, the motion converting member 5 is not operated. On the other hand, the rotation torque of the intermediate shaft 3 is transmitted to the clutch sleeve 25 by way of the first gear 10 and the second gear 26, and then, transmitted from the clutch sleeve 25 to the tool holding sleeve 11 by way of the second clutch 27, whereby only the rotary motion of the tip end tool 22 is carried out.

Further, FIG. 3 shows the hammer drill in the hammering mode. In this mode, the second clutch 27 retreats against the urge of the clutch spring 39 to be disengaged from the clutch sleeve 25, whereby transmission of the rotation from the clutch sleeve 25 to the tool holding sleeve 11 is interrupted, and hence, the tool holding sleeve 11 is not rotated. On the other hand, the rotation torque of the intermediate shaft 3 is transmitted to the motion converting member 5 only, and only the hammering motion of the tip end tool 22 is carried out.

By the way, switching between the above described three modes is conducted by operating a switch lever. Specifically, as shown in FIGS. 7 and 8, a body part 47 a of a switch lever 47 is rotatably provided on the housing 1. A lever part 48 is provided outside the body part 47 a, and a first switch shaft 50 and a second switch shaft 51 are provided at offset positions inside the body part. The first switch shaft 50 is so arranged as to be engaged with the first clutch 6. The second switch shaft 51 is so arranged as to be engaged with the second clutch 27 by way of a shift plate 52. As shown in FIGS. 9 and 10, the shift plate 52 is provided on an inner wall 53 of the housing 1 so as to move back and forth, and has a bent portion 54 at its front end and an actuating piece 55 in its middle part. An end of the bent portion 54 is engaged with the engaging groove 35 in the middle of the second clutch 27, while the actuating piece 55 is so arranged as to be engaged with the second switch shaft 51. Accordingly, by rotating the switch lever 47, the second switch shaft 51 is engaged with the actuating piece 55 and pushed in, whereby the shift plate 52 is moved, and at the same time, the second clutch 27 which is engaged with the bent portion 54 is moved to the right and left.

In FIG. 8, numeral 47 b represents a push button for restraining the switch lever 47 which has been set in a determined mode from arbitrarily rotating.

In the above described structure, when the motion mode is switched to the rotary hammering mode by operating the switch lever 47 to rotate, the first switch shaft 50 and the second switch shaft 51 are at respective positions as shown in FIG. 1, wherein the motion converting member 5 is connected to the intermediate shaft 3 by means of the first clutch 6, and the tool holding sleeve 11 is connected to the clutch sleeve 25 by means of the second clutch 27.

When the rotation mode is set by rotating the switch lever 47, the first switch shaft 50 moves the first clutch 6 backward against the urge of the clutch spring 9, as shown in FIG. 2, whereby transmission of the power from the intermediate shaft 3 to the motion converting member 5 is interrupted, while the clutch sleeve 25 is connected to the tool holding sleeve 11.

Further, when the hammering mode is set by rotating the switch lever 47, the second switch shaft 51 moves the second clutch 27 backward against the urge of the clutch spring 39, as shown in FIGS. 3, 9, and 10, whereby transmission of the power from the clutch sleeve 25 to the tool holding sleeve 11 is interrupted. On the other hand, the motion converting member 5 is connected to the intermediate shaft 3.

When the motion mode is again switched from the hammering mode to the rotation mode, the second clutch 27 is moved forward by the clutch spring 39, whereby the front teeth 36 of the second clutch 27 are meshed with the engaging claws 31 of the clutch sleeve 25. In this manner, the rotation of the intermediate shaft 3 is transmitted to the tool holding sleeve 11 thereby to rotate it.

In the hammering mode, the rear teeth 37 of the second clutch 27 are meshed with the teeth 44 of the lock bar 42, as shown in FIG. 6. In this case, even though the rear teeth 37 of the second clutch 27 are not smoothly meshed with the teeth 44 of the lock bar 42 due to interference between them, when the second clutch 27 moves backward, the clutch sleeve 25 can move to the determined position. Because the lock bar 42 is always urged forward by the spring 43 so as to be engaged, and the tool holding sleeve 11 is rotated, even a little, by the clutch sleeve 25 due to friction force between them, the teeth 44 of the lock bar 42 are smoothly engaged with the second clutch 27. In this manner, the tool holding sleeve 11 is maintained in a state restrained from rotating, and thus, fine-tuning of the tool becomes possible.

Moreover, the slanted convex parts 32 and the slanted concave parts 33 are formed in the flange 28 and the second gear 26 so as to be opposed to each other, as shown in FIGS. 5A and 5B, and urged so as to be meshed with each other by the clutch spring 34 (See FIG. 1). For example, in FIG. 1, in case where the tip end tool 22 is locked for some unexpected reason such as when the drill strikes a rebar in reinforced concrete, the clutch sleeve 25 is also locked, and the second gear 26 is pushed forward against the clutch spring 34 to be disengaged from the clutch sleeve 25. As the results, only the second gear 26 idly rotates and acts as a safety mechanism which absorbs the rotation of the intermediate shaft 3. Therefore, waving of the tool body will not occur.

As described above, the engagement between the first gear 10 and the second gear 26, and the engagement between the second clutch 27 and the tool holding sleeve 11 are always maintained irrespective of switching between the modes. Therefore, there is no problem of engagement between the gears, and smooth operation can be always secured.

In case where the second clutch 27 is disengaged from the clutch sleeve 25, the second clutch 27 is rapidly locked by the lock bar 42, since the lock bar 42 is always urged by the spring to be engaged. Therefore, it is possible to reliably stop the rotation of the tool holding sleeve 11.

In this manner, operation of the mode switching lever is ensured. It is also possible to lock the tool holding sleeve by fine-tuning it, by constructing the hammer drill in such a manner that the clutch sleeve 25 is moved for a determined distance to be meshed with the lock bar 42.

Although the invention has been described in detail referring to the specific embodiments, it would be apparent to those skilled in the art that various modifications and amendments can be added without departing spirit and scope of the invention.

The invention is based on Japanese Patent Application which was filed on Nov. 16, 2005 (Japanese Patent Application No. 2005-331660), the contents of which are hereby incorporated by reference.

INDUSTRIAL APPLICABILITY

The invention can be applied to a hammer drill in which motion mode can be switched between a hammering mode, a rotation mode, and a rotary hammering mode. 

1. A hammer drill comprising: an intermediate shaft coupled to a motor; a tool holding sleeve arranged in parallel with the intermediate shaft and configured to hold a tip end tool; a motion converting member provided on the intermediate shaft so as to rotate and configured to convert a rotary motion to a reciprocating motion; a first clutch provided between the intermediate shaft and the motion converting member; a clutch sleeve disposed on an outer periphery of the tool holding sleeve and coupled to the intermediate shaft by way of a rotation transmitting member; and a second clutch disposed on the outer periphery of the tool holding sleeve so as to rotate integrally with the tool holding sleeve and so as to move in a longitudinal direction of the tool holding sleeve and configured to be engaged with and disengaged from the clutch sleeve.
 2. The hammer drill according to claim 1, wherein the motion converting member converts the rotary motion of the intermediate shaft to the reciprocating motion to operate the tip end tool to hammer.
 3. The hammer drill according to claim 1, further comprising: a lock member capable of being engaged with the second clutch which has been disengaged from the clutch sleeve, wherein the lock member is urged in a direction so as to be engaged with the second clutch.
 4. The hammer drill according to claim 1, wherein a gear is formed at a front end of the intermediate shaft, the rotation transmitting member is always meshed with the gear at the front end of the intermediate shaft, and the rotation transmitting member is provided on an outer periphery of the clutch sleeve so as to rotate, and urged in a direction so as to be meshed with the clutch sleeve. 